1. Field of the Invention
The present invention relates to a powder-coated stator core, a coating method for the stator core, and a coating apparatus for the stator core, and more particularly to powder coating of a stator core of a vehicular rotary electric machine.
2. Description of the Related Art
FIG. 10 is a section view showing the configuration of a vehicular alternator, which is disclosed in, for example, JP-A-2001-238419. In FIG. 10, 1 denotes a front bracket, 2 denotes a rear bracket, 3 denotes a stator, which is interposed between the front bracket 1 and the rear bracket 2 and is configured by a stator core 4 and a stator coil 5, and 6 denotes a rotor. The rotor includes a rotation shaft 7 in which the both ends thereof are supported by the front bracket 1 and the rear bracket 2, respectively, rotor cores 8 and 9, which are attached to the rotation shaft 7, a field coil 10, which is wound between the rotor cores 8 and 9, fans 11 and 12, which are disposed on the back sides of the rotor cores 8 and 9, respectively, and a slip ring 13, which is disposed on the rotation shaft 7 to supply a current to the field coil 10.
The outer peripheries of the rotor cores 8 and 9 are opposed via an air gap to the inner periphery of the stator core 4. The reference numeral 14 denotes a pulley, which is disposed on the rotation shaft 7. The reference numeral 15 denotes a brush for supplying a current to the slip ring 13, 16 denotes a brush holder, which holds the brush 15, 17 denotes a three-phase full-wave rectifier, which rectifies the AC output of the stator coil 5, and 18 denotes a regulator, which adjusts the current of the field coil 10 to control the output voltage of the stator coil 5. These components are attached to the rear bracket 2. The stator coil 5, which is wound and inserted into the stator core 4, is extended toward the rear bracket 2, and a joining terminal 19 is welded to the tip end. The terminal is connected and fixed to a terminal 17a of the rectifier 17.
In the thus configured vehicular alternator, the stator 3 is formed by applying an insulating process on the stator core 4, and then inserting or winding the stator coil 5 on the stator core. The insulating process can be conducted by a method such as that insulating paper is interposed between the stator core 4 and the stator coil 5, or that powder coating for insulation is applied to the surface of the stator core 4. As disclosed in, for example, JP-A-Sho.57-135655, a method in which powder coating is conducted after a jig is mounted on the inner radial side of the stator core 4 to take a measure (masking) for preventing powder from adhering to a portion not to be powder-coated is usually employed as a method of producing a stator of a vehicular alternator or the like that is requested to be mass-produced at a lower cost.
The stator core 4 of the vehicular alternator is powder-coated as described above. When the number of the slots or the dimensions of the stator core are changed, therefore, the jig must be changed, and a work of replacing the jig with another one is necessary. When a large clearance is formed between the stator core 4 and the jig, masking may not be surely performed, thereby raising the possibility that powder adhering to the inner peripheral face of the stator core 4 rubs against the outer peripheral faces of the rotor cores 8 and 9. When the air gap is increased in order to cope with this, the performance of the alternator is lowered. Alternatively, a work of removing the excess powder adhering to the inner peripheral face of the stator core 4 must be additionally conducted. By contrast, when the clearance between the stator core and the jig is too small, the jig cannot be smoothly mounted or dismounted, and positioning between the jig and the stator core 4 must be conducted. Furthermore, the removal of powder adhering to the jig must be conducted after the jig is dismounted from the stator core 4. In this way, the method has also a problem with productivity.
In the method according to the related art in which the inner peripheral face of the stator core 4 is masked by the jig, powder can be applied only from the side of the axial end faces of the stator core 4. In the case where the slot area is reduced as a result of an increased number of slots or the axial length of the stator core 4 is prolonged, therefore, powder coating is ununiformly conducted in such a manner that, for example, the film thickness on the axial end faces of the stator core, 4 is large but that in a slot in the vicinity of the axial center is small. This causes a coil failure such as that the insulation property is lowered, that the stator coil 5 cannot be accommodated in the slots, or that the stator coil 5 is damaged. When a thin stator coil 5 is used in order to prevent such a failure from occurring, there arises a problem such as that the performance is lowered.